Ccna1 Mod7 Ethernet Technology

7/27/2019 Ccna1 Mod7 Ethernet Technology

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Module 7 - Ethernet Technologies

CCNA 1 version 3.1

Hc vin mng Cisco BchKhoa - Website: www.ciscobachkhoa.com

Contents

Describe the differences and similarities among 10BASE5,10BASE2, and 10BASE-T Ethernet.

Define Manchester encoding. List the factors affecting Ethernet timing limits. List 10BASE-T wiring parameters. Describe the key characteristics and varieties of 100-Mbps

Ethernet.

Describe the evolution of Ethernet. Explain the MAC methods, frame formats, and transmission

process of Gigabit Ethernet.

Describe the uses of specific media and encoding with GigabitEthernet.

Identify the pinouts and wiring typical to the variousimplementations of Gigabit Ethernet.

Describe the similarities and differences between Gigabit and10 Gigabit Ethernet.

Describe the basic architectural considerations of Gigabit and10 Gigabit Ethernet.


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Ethernet introduction

Ethernet has been the most successful LAN technologylargely because of its simplicity of implementation

compared to other technologies

The 10-Mbps Ethernet of the early 1980s. In 1995 IEEEannounced a standard for a 100 Mbps Fast Ethernet. In

recent years, a growth in media speed has moved the

transition from Fast Ethernet to Gigabit Ethernet. An

even faster Ethernet version, 10 Gigabit Ethernet, is

now widely available and still faster versions are being

developed.


10-Mbps Ethernet

10BASE5, 10BASE2, and 10BASE-T Ethernet are considered LegacyEthernet

The four common features of Legacy Ethernet are timing parameters,frame format, transmission process, and a basic design rule

The Legacy Ethernet transmission process is identical except the lowerpart of the OSI physical layer

Common timing parameters

Common frame format


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Signal Quality Error

Further processes occur prior to the bits being placed from the physical layer ontothe medium. One important process is the signal quality error (SQE) signal. SQE is

always used in half-duplex. SQE can be used in full-duplex operation but is not

required. SQE is active in case of :

1. Within 4 to 8 microseconds following a normal transmission to indicate

that the outbound frame was successfully transmitted

2. Whenever there is a collision on the medium3. Whenever there is an improper signal on the medium. Improper

signals might include jabber, or reflections that result from a cable

short.

4. Whenever a transmission has been interrupted


Manchester encoding

All 10 Mbps forms ofEthernet take octets received

from the MAC sublayer and

perform a process called line

encoding (describes how the

bits are actually signaled on

the wire)

This form of encoding usedin 10 Mbps systems is called

Manchester.

The direction of the edgetransition in the middle of the

timing window to determine

the binary value for that bit

period

Double

rate


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Timing limits, interoperability

Legacy Ethernet has common architectural features. The standard ensures thatinteroperability is maintained between multiple types of media. The overall

architectural design is of the utmost importance when implementing a mixed-

media network. The timing limits are based on below parameters should be

followed (as standards):

1. Cable length and its propagation delay2. Delay of repeaters3. Delay of transceivers4. Interframe gap shrinkage5. Delays within the station

5-4-3 rule

on 10Mbps Ethernet


10BASE5

10BASE5 was part of the original 802.3 standard (in 1980).The primary benefit of 10BASE5 was length.

10BASE5 systems was the past, not recommended for new installation today

(inexpensive and require no configuration, but basic components like NICs are very

difficult to find, it is sensitive to signal reflections on the cable, it represents a single

point of failure)

10BASE5 uses Manchester encoding, max. 500m per segment (large, heavy cablemakes it difficult to install)

10BASE5 only runs in half-duplex resulting in a maximum of 10 Mbps of datatransfer

500 m


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10BASE2

10BASE2 (in 1985) uses thin coaxial cable. Installation was easier because of itssmaller size, lighter weight, and greater flexibility.

It still exists in legacy networks. Like 10BASE5, it is not recommended forinstallations in networks today. (low cost and without using hubs), it also uses

Manchester encoding.

10BASE2 also uses half-duplex. The maximum transmission rate of 10BASE2 is10 Mbps.

There may be up to 30 stations on any individual 10BASE2 segment. Out of thefive consecutive segments in series between any two distant stations, only three

may have stations attached

185 m


10BASE-T

10BASE-T (in 1990) used cheaper and easier to install Category 3 unshielded twisted pair(UTP) copper cable rather than coax cable. The cable plugged into a central connection device(the shared bus), this device was a hub.

This is referred to as a star topology. The distances the cables could extend from the hub viaanother hub referred to as an extended star topology.

Originally 10BASE-T was a half-duplex protocol, but full-duplex features were added later.10BASE-T : Manchester encoding, max. 90 meter horizontal cable, use RJ-45 connectors

- UTP 3 cable is adequate BUT strongly recommended UTP 5e or better for new cable

installations. All four pairs of wires should be used either with the T568-A or T568-B

- this cable installation supports the use of multiple protocols without rewiring

- 10Mbps on half-duplex, 20Mbps on full


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10Base-T repeated network design limi ts

Hubs are multi-port repeaters and do not divide network segments into separate collision domains,there is a limit on how many hubs may be used in that segment.

Bridges and switches divide a segment into separate collision domains, 10BASE-T limits thedistance between switches to 100 m (328 ft)

Although hubs may be linked, it is best to avoid. This is to prevent exceeding the limit formaximum delay between distant stations. When multiple hubs are required, it is best to arrange

them in hierarchical order as to create a tree structure. Performance will be improved if using fewer

repeaters

A shorter maximum

delay will provide

better overall

performance


Parameters for 100Mbps Ethernet operation

100-Mbps Ethernet is also known as Fast Ethernet. The two technologies that havebecome important are 100BASE-TX, which is a copper UTP medium and 100BASE-

FX, which is a multimode optical fiber medium.

Three characteristics common to 100BASE-TX and 100BASE-FX are the timingparameters, the frame format, and parts of the transmission process. 100BASE-TX

and 100-BASE-FX both share timing parameters. Note that one bit time in 100-Mbps

Ethernet is 10nsec = .01 microseconds

The 100-Mbps frame

format is the same as

the 10-Mbps frame


7/18


Fast Ethernet represents a 10-fold increase in speed over

10BASE-T.

Because of the increase inspeed so the bits being sent are

getting shorter in duration and

occurring more frequently.

These higher frequency signalsare more susceptible to noise.

In response to these issues,two separate encoding steps are

used by 100-Mbps Ethernet.

The first part of the encoding

uses a technique called 4B/5B,

the second part of the encodingis the actual line encoding

specific to copper or fiber

Considerations for 100Mbps


100Mbps encoding

100BASE-TX uses 4B/5B encoding,which is then scrambled and converted

to multi-level transmit-3 levels or MLT-3

Pin-out for a 100BASE-TX connectionis identical to the 10BASE-T

configuration

100BASE-TX carries 100 Mbps oftraffic in half-duplex mode. In full-duplex

mode, 100BASE-TX can exchange 200

Mbps of traffic


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100Mbps on fiber

100BASE-FX was introduced to satisfybackbone links, connections between floorsand buildings, in high noise environments.

The timing, frame format, and transmissionare all common to both versions of 100 MbpsFast Ethernet. 100BASE-FX also uses 4B/5B

encoding100BASE-FX has 2 pins. Fiber pair witheither ST or SC connectors, separate Transmitand Receive paths allow up to 200 Mbps


Cable distances

Fast Ethernet links generallyconsist of a connection between

a station and a hub or switch.

These are subject to the 100 m

UTP media distance limitation

A Class I repeater mayintroduce up to 140 bit-times of

latency. Any repeater that

changes between one Ethernet

implementation and another is a

Class I repeater

A Class II repeater may onlyintroduce a maximum of 92 bit-

times latency. Because of the

reduced latency it is possible to

have two Class II repeaters in

series, but only if the cable

between them is very short (5m)


9/18


Gigabit and 10-Gigabit Ethernet

The 1000-Mbps Ethernet orGigabit Ethernet standardsrepresent transmission using

both fiber and copper media

The 1000BASE-X standard,IEEE 802.3z, specifies 1 Gbps

full duplex over optical fiber.

1000BASE-CX, 1000BASE-SX,and 1000BASE-LX use the

same timing parameters

The Gigabit Ethernet frame hasthe same format as is used for

10 and 100-Mbps Ethernet

Gigabit Ethernet may usedifferent processes to convert

frames to bits on the cable



The differences between standard Ethernet, Fast Ethernet and Gigabit Ethernetoccur at the physical layer. Due to the increased speeds of these newer

standards, the shorter duration bit times require special considerations. Since the

bits are introduced on the medium for a shorter duration and more often, timing is

critical. This high-speed transmission requires frequencies closer to copper

medium bandwidth limitations. This causes the bits to be more susceptible to

noise on copper media.


10/18



These issues require GigabitEthernet to use two separate

encoding steps.

Data transmission is mademore efficient by using codes to

represent the binary bit stream.

The encoded data provides

synchronization, efficient usage

of bandwidth, and improved

Signal-to-Noise Ratio

characteristics

At the physical layer, the bitpatterns from the MAC layer are

converted into symbols. The

symbols may also be controlinformation such as start frame,

end frame, medium idle

conditions

Fiber-based Gigabit Ethernet (1000BASE-X) uses8B/10B encoding, this is followed by the simple

Non-Return to Zero (NRZ) line encoding of light

on optical fiber


Gigabit Ethernet on copper

1000BASE-T (IEEE 802.3ab)was developed to provide

additional bandwidth.

1000BASE-T (CAT 5e)standard is interoperable with

10BASE-T and 100BASE-TX

(Fast Ethernet was designed to

function over Cat 5 copper

cable. Most installed Cat 5 cable

can pass 5e certification if

properly terminated)

Because Cat 5e cable canreliably carry up to 125 Mbps oftraffic, to get 1000 Mbps all four

pairs of wires are used and

using complex circuitry to allow

full duplex transmissions on the

same wire pair

Full duplex on each pair

All 4 pairs carry data


11/18



The 1000BASE-T encodingwith 4D-PAM5.

Transmission and reception ofdata happens in both directions

on the same wire at the same

time.

As might be expected, thisresults in a permanent collision

on the wire pairs. These

collisions result in complex

voltage patterns. With the

complex integrated circuits using

techniques such as echo

cancellation, Layer 1 Forward

Error Correction (FEC), andprudent selection of voltage

levels, the system achieves the

1Gigabit throughput.



In idle periods there are nine voltage levels found on the cable, and during datatransmission periods there are 17 voltage levels found on the cable

With this large number of states and the effects of noise, the signal on the wirelooks more analog than digital. Like analog, the system is more susceptible to noise

due to cable and termination problems

1000BASE-T supports both half-

duplex as well as full-duplex

operation

data from the sending station is

carefully divided into four parallel

streams, encoded, transmitted

and detected in parallel, and then

reassembled into one received bit

stream


12/18


Gigabit Ethernet on fiber

The IEEE 802.3 standard recommends that Gigabit Ethernet over fiber be thepreferred backbone technology

The timing, frame format, and transmission are common to all versions of 1000Mbps

Two signal-encoding schemes are defined at the physical layer The 8B/ 10B scheme is used for optical fiber and shielded copper media

The pulse amplitude modulation 5 (PAM5) is used for UTP



1000BASE-X uses 8B/10Bencoding converted to non-

return to zero (NRZ) line

encoding (level of signal

determines 1 or 0)

NRZ signals are then pulsedinto the fiber using either short-

wavelength or long-wavelength

light sources

The light is pulsed using low(as 0) and high power (as 1)

Laser or LED source

Multi Mode Fiber

Laser source,

Single

Mode/Multi

Mode Fiber


13/18



The Media Access Control method treats the link as point-to-point.Since separate fibers are used for transmitting (Tx) and receiving (Rx)the connection is inherently full duplex.

Gigabit Ethernet permits only a single repeater between two stations



The distance limitations of full-duplex links are only limited by the medium, and notthe round-trip delay

Daisy-chaining, star, and extended star topologies are all allowed1000BASE-T UTP cable is the same as 10BASE-T and 100BASE-TX cable, exceptthat link performance must meet the higher quality ( 5e or ISO Class D (2000))

(1000BASE-T is operating close to the edge of the ability of the hardware any cabling

problems or environmental noise could make it inoperable

Since most Gigabit Ethernet is

switched the values are the

practical limits between

devices

links between a station and a

hub or switch should be

configured for Auto-

Negotiation


14/18


10 Gigabit Ethernet

10GbE physical layer standards allow both an extension in distance to 40 km oversingle-mode fiber and compatibility with synchronous optical network (SONET) and

synchronous digital hierarchy (SDH) networks. Operation at 40 km distance makes

10GbE a viable MAN technology. Compatibility with SONET/SDH networks

operating up to OC-192 speeds (9.584640 Gbps) make 10GbE a viable WAN

technology. 10GbE may also compete with ATM for certain applications


10 Gigabit Ethernet

IEEE 802.3ae was adapted to include 10 Gbps full-duplex transmission over fiberoptic cable. The basic similarities between 802.3ae and 802.3, the original Ethernet

are remarkable. This 10-Gigabit Ethernet (10GbE) is evolving for not only LANs, but

also MANs, and WANs

With the frame format and other Ethernet Layer 2 specifications compatible withprevious standards, 10GbE can provide increased bandwidth needs that are

interoperable with existing network infrastructure


15/18


10GbE compares to other varieties of Ethernet

Frame format is the same, allowing interoperability between allvarieties of legacy, fast, gigabit, and 10 Gigabit, with no reframing or

protocol conversions.

Bit time is now 0.1 nanoseconds. All other time variables scaleaccordingly.

Since only full-duplex fiber connections are used, CSMA/CD is notnecessary

The IEEE 802.3 sublayers within OSI Layers 1 and 2 are mostlypreserved, with a few additions to accommodate 40 km fiber links and

interoperability with SONET/SDH technologies.

Flexible, efficient, reliable, relatively low cost end-to-end Ethernetnetworks become possible.

TCP/IP can run over LANs, MANs, and WANs with one Layer 2Transport method.


Variety of implementations 10GbE

10GBASE-SR Intended for short distances over already-installedmultimode fiber, supports a range between 26 m to 82 m

10GBASE-LX4 Uses wavelength division multiplexing (WDM),supports 240 m to 300 m over already-installed multimode fiber and

10 km over single-mode fiber

10GBASE-LR and 10GBASE-ER Support 10 km and 40 km oversingle-mode fiber

10GBASE-SW, 10GBASE-LW, and 10GBASE-EW Knowncollectively as 10GBASE-W are intended to work with OC-192

synchronous transport module (STM) SONET/SDH WAN equipment.


16/18


10-Gigabit Ethernet architectures

For 10 GbE transmissions, each data bit duration is 0.1nanosecond

Because of the short duration, it is often difficult to separate a databit from noise. 10 GbE data transmissions rely on exact bit timing

to separate the data from the effects of noise on the physical layer.

10-Gigabit Ethernet uses two separate encoding steps. By usingcodes to represent the user data, transmission is made more

efficient. The encoded data provides synchronization, efficient

usage of bandwidth, and improved Signal-to-Noise Ratio

characteristics



Complex serial bit streams are used for all versions of 10GbE except for 10GBASE-LX4, which uses Wide Wavelength Division Multiplex (WWDM) to multiplex four bitsimultaneous bit streams as four wavelengths of light launched into the fiber at one time

All 10GbE varieties use optical fiber media. Fiber types include 10 single-mode Fiber,and 50 and 62.5 multimode fibers. A range of fiber attenuation and dispersioncharacteristics is supported, but they limit operating distances

WDM example


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No repeater is defined for 10-Gigabit Ethernet since half duplex isexplicitly not supported

Some of the maximum cable lengths are surprisingly short

Fiber optic length


Future of Ethernet

Recently developing versions of Ethernet are blurringthe distinction between LANs, MANs, and WANs

IEEE and the 10-Gigabit Ethernet Alliance are workingon 40, 100, or even 160 Gbps standards

Using UTP and optical fiber with separate Tx and Rxpaths, and the decreasing costs of switches make

single shared media, half-duplex media connections

much less important

The full-duplex high-speed Ethernet technologies that

now dominate the market are proving to be sufficient at

supporting even QoS-intensive applications


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Summary

The differences and similarities among 10BASE5, 10BASE2, and10BASE-T Ethernet

Manchester encoding

The factors affecting Ethernet timing limits

10BASE-T wiring parameters

The key characteristics and varieties of 100-Mbps Ethernet

The evolution of Ethernet

MAC methods, frame formats, and transmission process of GigabitEthernet

The uses of specific media and encoding with Gigabit Ethernet

The pinouts and wiring typical to the various implementations of GigabitEthernet

The similarities and differences between Gigabit and 10-GigabitEthernet

The basic architectural considerations of Gigabit and 10-GigabitEthernet

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